let obj = { name: '许嵩', num: 25 }

const singer = [
    { name: '周杰伦', num: 20 },
    obj,
    { name: '林俊杰', num: 19 },
    { name: '蔡徐坤', num: 10 },
    { name: '鹿晗', num: 0 },
]

const nums = [1, 2, 3, 4, 5, NaN]

Array.prototype.my_includes = function (val, start = 0) {
    if (start < 0) start = this.length + start
    const isNaN = Number.isNaN(val)

    for (let i = start; i < this.length; i++) {
        if (this[i] === val || (isNaN && Number.isNaN(this[i]))) {  // NaN !=== NaN
            return true
        }
        return false
    }
}

const res = singer.includes(NaN, 0)

console.log(res);